/************************************************************************
 * Strathclyde Planning Group, Department of Computer and Information Sciences,
 * University of Strathclyde, Glasgow, UK http://planning.cis.strath.ac.uk/
 * 
 * Copyright 2007, Keith Halsey Copyright 2008, Andrew Coles and Amanda Smith
 * 
 * (Questions/bug reports now to be sent to Andrew Coles)
 * 
 * This file is part of JavaFF.
 * 
 * JavaFF is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 2 of the License, or (at your option) any later
 * version.
 * 
 * JavaFF is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * JavaFF. If not, see <http://www.gnu.org/licenses/>.
 * 
 ************************************************************************/

package javaff.search;

import java.util.Hashtable;
import java.util.LinkedList;

import javaff.planning.FFState;
import javaff.planning.Filter;

public class BreadthFirstSearch extends Search {

	protected LinkedList	open;
	protected Hashtable		closed;
	protected Filter		filter	= null;

	public BreadthFirstSearch(FFState s) {
		super(s);
		open = new LinkedList();
		closed = new Hashtable();
	}

	public void setFilter(Filter f) {
		filter = f;
	}

	public void updateOpen(FFState S) {
		open.addAll(S.getNextStates(filter.getActions(S)));
	}

	public FFState removeNext() {
		return (FFState) (open).removeFirst();
	}

	public boolean needToVisit(FFState s) {
		Integer Shash = new Integer(s.hashCode());
		FFState D = (FFState) closed.get(Shash);

		if (closed.containsKey(Shash) && D.equals(s))
			return false;

		closed.put(Shash, s);
		return true;
	}

	@Override
	public FFState search() {

		open.add(start);

		while (!open.isEmpty()) {
			FFState s = removeNext();
			if (needToVisit(s)) {
				++nodeCount;
				if (s.goalReached()) {
					return s;
				} else {
					updateOpen(s);
				}
			}

		}
		return null;
	}

	public int getNodeCount() {
		return nodeCount;
	}

}
